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            <small>
              <a href="#Procedure">Procedure<br></a>
              <a href="#Abstract">Abstract<br></a>
              <a href="#Required_Reading">Required_Reading<br></a>
              <a href="#Keywords">Keywords<br></a>
              <a href="#Brief_I/O">Brief_I/O<br></a>
              <a href="#Detailed_Input">Detailed_Input<br></a>

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              <small>               <a href="#Detailed_Output">Detailed_Output<br></a>
              <a href="#Parameters">Parameters<br></a>
              <a href="#Exceptions">Exceptions<br></a>
              <a href="#Files">Files<br></a>
              <a href="#Particulars">Particulars<br></a>
              <a href="#Examples">Examples<br></a>

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              <small>               <a href="#Restrictions">Restrictions<br></a>
              <a href="#Literature_References">Literature_References<br></a>
              <a href="#Author_and_Institution">Author_and_Institution<br></a>
              <a href="#Version">Version<br></a>
              <a href="#Index_Entries">Index_Entries<br></a>
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<h4><a name="Procedure">Procedure</a></h4>
<PRE>
   void nplnpt_c ( ConstSpiceDouble    linpt  [3],
                   ConstSpiceDouble    lindir [3],
                   ConstSpiceDouble    point  [3],
                   SpiceDouble         pnear  [3],
                   SpiceDouble       * dist       ) 

</PRE>
<h4><a name="Abstract">Abstract</a></h4>
<PRE>
 
   Find the nearest point on a line to a specified point, and find 
   the distance between the two points. 
 </PRE>
<h4><a name="Required_Reading">Required_Reading</a></h4>
<PRE>
 
   None. 
 </PRE>
<h4><a name="Keywords">Keywords</a></h4>
<PRE>
 
   GEOMETRY 
   MATH 
   VECTOR 
 

</PRE>
<h4><a name="Brief_I/O">Brief_I/O</a></h4>
<PRE>
 
   Variable  I/O  Description 
   --------  ---  -------------------------------------------------- 
   linpt, 
   lindir     I   Point on a line and the line's direction vector. 
   point      I   A second point. 
   pnear      O   Nearest point on the line to point. 
   dist       O   Distance between point and pnear. 
 </PRE>
<h4><a name="Detailed_Input">Detailed_Input</a></h4>
<PRE>
 
   linpt 
   lindir         are, respectively, a point and a direction vector 
                  that define a line in 3-dimensional space.  The 
                  line is the set of points 
 
                     linpt   +   t * lindir 
 
                  where t is any real number. 
 
   point          is a point in 3-dimensional space. 
 </PRE>
<h4><a name="Detailed_Output">Detailed_Output</a></h4>
<PRE>
 
   pnear          is the nearest point on the input line to the input 
                  point. 
 
   dist           is the distance between the input line and input 
                  point. 
 </PRE>
<h4><a name="Parameters">Parameters</a></h4>
<PRE>
 
   None. 
 </PRE>
<h4><a name="Exceptions">Exceptions</a></h4>
<PRE>
 
   1)  If the line direction vector lindir is the zero vector, the 
       error SPICE(ZEROVECTOR) is signaled. 
 </PRE>
<h4><a name="Files">Files</a></h4>
<PRE>
 
   None. 
 </PRE>
<h4><a name="Particulars">Particulars</a></h4>
<PRE>
 
   For every line L and point P, there is a unique closest point 
   on L to P.  Call this closest point C.  It is always true that 
   P - C  is perpendicular to L, and the length of P - C is called 
   the &quot;distance&quot; between P and L. 
 </PRE>
<h4><a name="Examples">Examples</a></h4>
<PRE>
 
   1)  Suppose a line passes through the point ( 1, 2, 3 ) and 
       has direction vector ( 0, 1, 1 ).  We wish to find the 
       closest point on the line to the point ( -6, 9, 10 ).  We 
       can use the code fragment 
 
          #include &quot;SpiceUsr.h&quot;
               .
               .
               .
          LINPT[0]   =  1.0; 
          LINPT[1]   =  2.0; 
          LINPT[2]   =  3.0; 
 
          LINDIR[0]  =  0.0; 
          LINDIR[1]  =  1.0; 
          LINDIR[2]  =  1.0; 
 
          POINT[0]   = -6.0; 
          POINT[1]   =  9.0; 
          POINT[2]   = 10.0; 
 
          <b>nplnpt_c</b> ( linpt, lindir, point, pnear, &amp;dist );
 
 
       After the call, pnear will take the value 
 
          ( 1., 9., 10. ); 
 
       dist will be 7.0. 
 </PRE>
<h4><a name="Restrictions">Restrictions</a></h4>
<PRE>
 
   None. 
 </PRE>
<h4><a name="Literature_References">Literature_References</a></h4>
<PRE>
 
   None. 
 </PRE>
<h4><a name="Author_and_Institution">Author_and_Institution</a></h4>
<PRE>
 
   N.J. Bachman   (JPL) 
 </PRE>
<h4><a name="Version">Version</a></h4>
<PRE>
 
   -CSPICE Version 1.0.0, 16-AUG-1999 (NJB)
</PRE>
<h4><a name="Index_Entries">Index_Entries</a></h4>
<PRE>
 
   distance between point and line 
   nearest point on line to point 
 </PRE>
<h4>Link to routine nplnpt_c source file <a href='../../../src/cspice/nplnpt_c.c'>nplnpt_c.c</a> </h4>

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   <pre>Wed Jun  9 13:05:27 2010</pre>

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